Quarterly report pursuant to Section 13 or 15(d)

Stock-Based Payments - Summary of Status of Stock Options and Changes During the Period (Details)

v3.19.1
Stock-Based Payments - Summary of Status of Stock Options and Changes During the Period (Details) - USD ($)
$ / shares in Units, $ in Thousands
3 Months Ended 12 Months Ended
Mar. 31, 2019
Dec. 31, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]    
Outstanding at beginning of year (in shares) 3,732,643  
Granted and outstanding (in shares) 953,800  
Exercised (in shares) (1,077)  
Cancelled (in shares) (68,971)  
Outstanding at end of period (in shares) 4,616,395 3,732,643
Exercisable (in shares) 1,726,979  
Outstanding at beginning of year (in dollars per share) $ 9.88  
Granted (in dollars per share) 6.78  
Exercised (in dollars per share) 2.86  
Cancelled (in dollars per share) 11.71  
Outstanding at end of period (in dollars per share) 9.21 $ 9.88
Exercisable (in dollars per share) $ 8.82  
Remaining Contractual Life, Outstanding 8 years 2 months 12 days 7 years 10 months 24 days
Remaining Contractual Life, Exercisable 7 years  
Aggregate Intrinsic Value, Outstanding $ 6,335 $ 1,694
Aggregate Intrinsic Value, Options Exercisable $ 3,362